A simple gamma irradiation strategy was developed for the synthesis of gold nanoplates by employing polydiallyldimethylammonium chloride (PDDA) as the capping agent. The nanoplates produced had hexagonal, triangular and truncated triangular shapes and the size of the nanoplates could be varied from 500 nm to 5 μm by adjusting the concentration of Au³⁺ and PDDA in the solution. X-ray diffraction and selected area electron diffraction investigations proved that the nanoplates are single crystals bound by the {111} planes on the top and bottom surfaces. The nanoplates were also characterized by energy dispersive X-ray analysis and X-ray photoelectron spectroscopy.